The present invention relates to a cooling box adapted to be installed in the refractory wall of a steel-making arc furnace for cooling the furnace wall.
In recent years, high power is supplied to steel-making arc furnaces to shorten the melting time and achieve improved efficiency. For example, arc furnaces of the standard type are equipped with a transformer for giving 300 kva/ton, while super-large furnaces are provided with a transformer with a capacity of 600 kva/ton.
Accordingly the heat of arc locally causes serious damage to the lining wall of the furnace at a so-called hot spot where the wall is opposed to the electrode. The furnace wall is also subject to marked damage or errosion in the vicinity of the slag line. Cooling boxes are therefore installed in the refractory wall of the furnace at such locations.
While cooling boxes of steel are generally used for this purpose, the steel box involves the problem that cracks are liable to develop therein owing to thermal and mechanical stress concentration when it is installed in the hot spot or in the neighborhood of the slag line. Such cracks will permit leakage of the cooling medium, possibly leading to an explosion accident, so that the cooling box must be repaired with a great expenditure and much labor.